P2 Flashcards
(46 cards)
1
Q
What are photo cells?
A
they are flat silicon surfaces that can capture the suns energy
2
Q
How do photocells work?
A
- light energy is absorbed by the photocell
- this causes the electrons in the crystals (in the photocell)to be knocked off of the silicon atoms
- this means that they can now move freely within the silicon creating electricity
( - this movement of free electrons is called an electrical current)
3
Q
What are the 3 things a photocell depends on?
A
- the surface area exposed to the light
- the intensity of the light
- the distance between the light source and the photocell
4
Q
What are 3 things the suns energy can be used for (apart form photocells)?
A
- light can be transformed into heat energy (used to heat up homes)
- a curved mirror can focus and intensify the suns light
- passive solar heating
5
Q
What is passive solar heating?
A
this is like the work of greenhouse - it traps energy from the sun but doesn’t change or distribute the energy
- this is what makes conservatories hot in the summer (doesn’t need photocells or any other devices)
6
Q
How does heating conservatories work?
A
- the visible light and infrared rays are absorbed by the objects in the room
- the objects then let off the infrared rays but it then cant get back through the conservatories glass as the rays now have longer wavelengths
- the infrared rays are then reflected back into the room to cause it to heat up
7
Q
How do wind turbines work?
A
- the suns energy produces convection currents in the air (i.e wind)
- the air carries Kinetic Energy and when the wind is caught by the wind turbines that Kinetic Energy is turned into electrical energy
8
Q
What is the dynamo effect?
A
- this is when a magnet moves towards a coil of wire or when a coil of wire moves towards a magnet
- when this happens the wire cuts and breaks through the magnetic field of the magnet and its current
- this then creates an electromagnetic induction in the wire
- it completes the circuit
(this will not work if the circuit is part of a complete circuit)
9
Q
How can the current in the dynamo effect be increased?
A
- using stronger magnets
- using more turns in the coil
- moving the coil faster
- moving the magnet faster
10
Q
How does an AC (alternating current) generator work?
A
- in the generator a coil of wire is rotated in a magnetic field (the coil and the field should be close together)
- as the coil breaks through the magnetic field the ‘relative motion’ (in reflection of one another) causes a current to be generated in the coil
- the current alternates (i.e it reverses its direction of flow) every half turn of the coil so the generator produces an ALTERNATING CURRENT (AC)
(this is different from battery which produces a direct current - DC)
11
Q
How is electricity produced in power stations?
A
- the fuel (energy source) is burned to release heat energy
- the heat boils water to produce steam
- the steam drives the turbines which then drives the generators
- the generators produce electricity
12
Q
What is the network of power lines called?
A
The National Grid
13
Q
What is the overall percentage of efficiency of power station’s energy?
A
30%
14
Q
What are the 3 greenhouse gases?
A
- carbon dioxide
- water vapour
- methane
15
Q
Why does the greenhouse effect occur?
A
- short wavelength electromagnetic radiation from the Sun is absorbed by Earth, causing it to heat up
- the Earth then radiates heat as longer wavelength infrared radiation which is sometimes absorbed by the greenhouse gases causing the Earth to heat up more so
16
Q
What are the 3 types of fuels that are commonly used in power stations?
A
- fossil fuels (crude oil, natural gas, coal)
- biomass (wood, straw, manure)
- nuclear fuel (uranium)
17
Q
What is the voltage of the electricity that is transmitted by the National Grid? Why?
A
about 40,000V (to reduce heat loss and costs)
- a higher voltage means a lower current, this means less energy is lost from the wires as heat
18
Q
What is used to increase and decrease the voltage before and after transmissions of electricity? Why are they used?
A
transformers
- they are used to decrease the voltage so that it is not too dangerous for the consumers (these are called ‘step-down transformers’)
19
Q
What are the 4 types of renewable sources for producing electricity?
A
- wind
- tidal
- hydroelectric (water)
- sun
20
Q
What is power measured in?
A
Watts or Kilowatts
21
Q
What is radioactivity?
A
it involves the change in structure of the radioactive atom and the release of one or more of the 3 types of nuclear radiation
22
Q
What are the 3 types of nuclear radiation?
A
- alpha
- beta
- gamma
23
Q
What is background radiation?
A
the radiation that occurs naturally around us
only very small so it doesn’t cause any damage to our health
24
Q
What is penetrative power?
A
what the different types of radiation can pass through, i.e different thickness’ due to their strength
25
What can Alpha Beta and Gamma radiation cause?
- it causes ionisation that can damage ' healthy molecules in living cells
- this can result in the death of a cell
- can also lead to cancer
26
What is Alphas ionising and penetration power?
- its ionising power is very strong (very dangerous)
| - cant even get through a few cm of air or thin paper
27
What is Betas ionising and penetration power?
- its ionising power is reasonable (a little dangerous but not fatal)
- can pass through air and paper, cant get through a few mm of aluminium
28
What is Gammas ionising and penetration power?
- its ionising power is weak
| - can basically get through anything: needs many cm of lead or metres of concrete to stop it
29
What happens during ionisation?
- a particle gains or loses an electron, this leaves the atom charged
- a gain in electron it becomes a negative ion
- a loss in electron it becomes a positive ion
30
used What are Alpha particles used for? Why/how?
- alpha particles can be used for smoke detectors
- the smoke detector emits alpha radiation
- this alpha radiation then ionises the air particles around the smoke detector
- the ions that are then formed are attracted to the oppositely charged electrodes
- on one side of the smoke detector there are negative electrodes and on the other side there are positive electrodes
- the negative ions are attracted to the positive electrodes
- the positive ions are attracted to the negative electrons
- this completes the circuit causing an electrical current
- when smoke enters the space between the different sides of the smoke detector it stops ionisation which then triggers an alarm
31
What are Beta particles used for? Why/how?
Beta particles are used in tracers
- a tracer is a small amount of radioactive substance that is put into a system so that its progress can be detected by a radiation detector
- a Beta emitter tracer can be used to observe elements (such as nitrogen and phosphorus) movements in plants
Beta particles can also be used in a paper thickness gauge
- this means that beta radiation can be emitted to be absorbed by some paper, if the paper is too thick then there will be more beta radiation being absorbed, if it is too thin then not a lot of beta radiation will be absorbed
32
What is Gamma radiation used for? Why/how?
- Gamma radiation can be used to treat cancer as it destroys cancerous cells (must be careful not to kill healthy cells)
- it can also be used to sterilise medical equipment as it can destroy microorganisms like bacteria
33
What are the 4 main problems when dealing with radioactive waste?
- the amount that is deemed acceptable may change over time
- needs to be kept away from ground water as it can contaminate water supplies
- can be a target for terrorist activity
- it remains radioactive for a very long time and must be disposed of safely
34
What are the 6 things the universe is made up of?
- comets
- meteors
- planets
- stars
- black holes
- galaxies
35
What are black holes and where can they be found?
- they are things that have a very large mass all concentrated into a very small space
- this means their gravity is very large (this is why nothing can escape from then - not even light)
- they can be found throughout the universe and in every galaxy
36
What is the order of the planets?
- Mercury
- Venus
- Earth
- Mars
- Jupiter
- Saturn
- Uranus
- Neptune
- Pluto (known as a dwarf planet)
37
How do the planets orbit each other?
- the force is provided by gravity and is called the centripetal force
- you could also say that the planets stay in orbit because of the gravitational force
38
What are the advantages and disadvantages of unmanned space travel?
advantages -
- costs are lower as there is no demand for food water and oxygen
- safety is no longer a worry as there are no humans aboard
disadvantages -
- reliability has to be high as no one will be there to fix breakdowns
- instruments must require no maintenance
39
What are asteroids? Where can you find them?
- they are rocks left over from the formation of the Solar System
- they normally orbit the Sun in the space between Mars and Jupiter but sometimes they can be knocked off course and be sent to earth
40
Why do we think the Earth has been hit by asteroids before?
- craters are found all over the planet
- there are layers of unusual elements found in rocks
- there are sudden changes in the amount of fossil fuels in rock layers due to a sudden death of many animals
41
Why cant asteroid conjoin to make a new planet?
because they will make up a large mass which is then pulled towards Jupiter as it has a strong gravitational field
- this means that they are attracted to it and as a consequence they break up again causing more asteroids
42
What is a comet? Where do they come from?
it is a small body with a core of frozen gas (ice) and dust
(many people know that comets have tails - this is just the debris of the dust and ice of the comet)
- they come from objects that orbit the Sun
- the speed of the comet increases as it gets closer to the sun (this is due to the increase in the strength of the gravity)
43
What are NEO's and what does it stand for?
- NEO stands for Near Earth Objects
| - they are comets or asteroids on a possible collision course with Earth
44
What does trajectory mean?
probable path
| - e.g a comet has a trajectory for Earth
45
How do we think the moon was formed?
- planets collided
| - the less dense materials of those planets come together and form the moon as it begins to orbit another planet
46
What is the Red Shift?
- this is the shifting of the wavelengths of light towards the red end of the spectrum
- the further away the galaxy is to us the greater the red shift is
- this provides evidence for the Expansion of the Universe
